Return Value

the last modification time of the region or the entry;
returns 0 if the entry is invalid or the modification time is uninitialized.

Remarks

The modification may have been initiated locally, or it may have been
an update distributed from another cache. It may also have been a new
value provided by a loader. The modification time on a region is
propagated upward to parent regions, transitively, to the root region.

The number is expressed as the number of milliseconds since January 1, 1970.
The granularity may be as coarse as 100ms, so the accuracy may be off by
up to 50ms.

Entry and subregion creation will update the modification time on a
region, but Region.Destroy, Region.DestroyRegion,
Region.Invalidate, and Region.InvalidateRegion
do not update the modification time.